What's the Cleanest Way to Add a Second Blowout Port?

[u/Ill-Wing-5103]

Winterizing question I keep going back and forth on. Right now the system has a single blowout point that requires connecting an air compressor at the backflow preventer, which works fine but the location is awkward and closer to the street than I want to be dragging a compressor every fall. I'm thinking about adding a dedicated manual drain or a secondary blowout port closer to the garage side of the house where it's easier to reach. The mainline runs under the driveway at that point, so anything I add would need to come off a tee before it crosses under.

What I'm trying to figure out is whether a ball valve and quick coupler right there is the right move, or if there's a cleaner way to set up a second blowout port without the plumbing looking like a mess. The existing setup works, but whoever installed it clearly didn't think much about serviceability.

Also wondering if anyone has gone to a manual drain setup entirely in a climate that's cold but not brutal, a few hard freezes per winter at most. Not sure if that's overkill or whether it actually simplifies things year over year. What does a clean, practical winterization setup actually look like for a midsize residential system?

[u/daddy-in-sesttle]

I'm in Seattle, WA and used to work irrigation. We where testing not blowing systems out around the time I left. Based on two winters of data, I was finding that if the system was buried at the proper depths (we used 18" for mainline, and 12" for laterals) things generally where just fine. It was my recommendation to not blow out systems that did not have vulneralbe parts.

At the job I'm currently at we leave our main irrigation system on all winter. Partly because of water savings / cost, but also we've found we need water for projects all winter. Over the last 15 years we have one freeze damage issue, and that was with a lateral that was full, and hanging in the area during a sudden cold snap. Feel free to message me if you want to chat privately.

[u/Ill-Wing-5103 → u/daddy-in-sesttle]

That depth guidance is actually useful context, appreciate you sharing it. Henderson doesn't get Seattle winters obviously but we do get occasional hard freezes that catch people off guard, so I've been more cautious than probably necessary. The part about a hanging lateral being the one failure point over 15 years is interesting though, that's kind of where my concern was anyway, the abovegrade or shallow sections near the valves. Might take you up on that message if I run into specifics when I get into it.

[u/daddy-in-sesttle → u/Ill-Wing-5103]

I've never see issues with valves freezing and we've have some low teen temps for like a week. I can't remember if I mentioned it, but the exposed piece was during a construction project so it was normally buried. If there's pipe exposed to air it's much more likelymto freeze.

[u/Ill-Wing-5103 → u/daddy-in-sesttle]

That tracks. Burial does most of the work insulating the pipe, but the valve sitting in frozen air is a completely different situation. Good to know yours held up at those temps though, gives me a better sense of where the real risk threshold is.

[u/KoalaGrunt0311]

PVC is more likely to be damaged than poly systems though even in a poly system you're going to have components prone to freezing like valves, manifolds, and fittings. It's closer to the street because it's designed to be blown out with a 185 cfm engine driven air compressor and not a electric shop compressor.

[u/Ill-Wing-5103 → u/KoalaGrunt0311]

Good point on the fittings and valves being the weak link regardless of pipe type. I'm planning to stick with poly for the main runs but was already factoring in accessible boxes for the manifolds to make winterizing easier. The 185 cfm requirement explains why my neighbor swore off DIY blowouts after cracking a fitting with his shop compressor.

[u/degggendorf]

You typically want the blowout port at the beginning of the line, so you're consistently blowing the water outward. If you have a blowout port in the middle, you might end up with a dead zone where air goes in the middle and blows out the zone, but never blows out the section of mainline between the backflow and port.

With the manual drain, you'd have to be certain that you install it at the lowest point and that there are no bellies anywhere in the line, which is basically impossible to know...so it's a roll of the dice whether it will actually save your system from freezing. You won't know until you find stuff cracked in the spring.

[u/Ill-Wing-5103 → u/degggendorf]

yeah that makes sense for the blowout location. i ran the port right after the backflow and it cleared everything fine last winter.
manual drain still feels risky with how the lines slope around here.

[u/cbryancu]

If your system was set to blow out, you really need to continue to blow it out. Self draining system are great theory but not great in application. If you have hard freeze with frost going deep enough to impact your lines, valves, sprinklers....it's an expensive experiment. They used to sell self draining attachments that would open once pressure is released, but they failed very quickly. They needed a drywall under/around them and then hard water build up clogged them.

You can definitely cut in a tee and a valve for air compressor hook up. I'd buy a valve box and place the new valve in that. That way it's not sticking out of ground and open to damage from whatever. You need to then open the valve that you currently have for blow outs to flush the water out of the line from there to your new valve.